Bosch dishwasher heating problem

[Chris Monk]

My Bosch Classixx Slimline dishwasher (SPS40C12GB about 4 years old) has three heat settings for washing...
70 degrees Intensive, which works fine
45 degrees Quick, which also works fine...
But
The ECO 50 degrees washes as normal, but does not heat the water. Everything else in this wash is as expected, but no hot water.
Since two of the washes work ok, I thought the heater element must be ok. So I guess I'm down to the thermostat or the PCB ? Does the thermostat have three connections, one for each temperature? Any ideas anyone before I go deeper in taking the poor machine apart?
Thanks.

 

[HERTS P&D]

see below:

http://www.boschdishwashertroubleshooting.com/

Andy

 

[Chris Monk]

My problem is Andy, all the advice I have read assumes that the dishwasher does not heat on any setting. Mine works on two of the three settings but not on ECO 45 deg, so much of what I read does not apply. Would like to understand how the thermostat works on three values however, but alas no technical diagrams etc are online.

 

[yardie]

could it possibly be to do with the dirty water sensor?

though if your model has a heat pump fitted I suspect thats the most likely culprit.

model no. should end with '/' and 2 digits